1. Technical Field
The present invention relates to a semiconductor light-emitting element, an electrode structure and a light-emitting device.
2. Related Art
The semiconductor light-emitting elements having a laminated semiconductor layer in which an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer composed of a group III-V compound semiconductor or a group II-IV compound semiconductor are widely used.
Recently, a GaN-based compound semiconductor has become a focus of attention as a semiconductor material of the light-emitting element of short wavelength light. The GaN-based compound semiconductor is formed by a metal organic chemical vapor deposition method (MOCVD method), a molecular beam epitaxy method (MBE method) or the like on a substrate composed of a sapphire single crystal or other various oxides or group III-V compounds.
In such a semiconductor light-emitting element using the GaN-based compound semiconductor, generally, a laminated semiconductor layer having an LED structure constituted by an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer is formed on a substrate, and while a transparent electrode and a pad electrode for bonding are formed on the p-type semiconductor layer on the top portion, another pad electrode for bonding is formed on the n-type semiconductor layer that has been exposed by removing part of the p-type semiconductor layer and the light-emitting layer by etching or the like.
As a related art, Japanese Patent Application Laid-Open Publication No. 2005-210050 describes that uppermost layers of a pad electrode on a transparent electrode layer and a pad electrode on an n-type semiconductor layer are composed of Au.
Here, generally in the case where a light-emitting device incorporating such a semiconductor light-emitting element is produced, each pad electrode is subjected to wire bonding using a known wire bonder. In the wire bonding, a bonding wire composed of Au or the like is connected to the uppermost layer of an electrode pad by applying a predetermined pressure to each electrode pad. When wire bonding is performed, there have been some cases where the pressure reaches a lower layer of the electrode pad or a transparent electrode layer or the like on which the electrode pad is laminated, and thereby separation of the electrode pad or cracks in the transparent electrode layer are caused.
It is an object of the present invention to improve joining properties of electrodes and reliability of the electrodes for supplying electrical power to a semiconductor.